Polyp detection in body cavities such as the abdomen or colon is typically performed by a trained professional making a visual inspection of the cavity. A fixed or a flexible endoscope is inserted into the cavity, and the endoscope both illuminates the cavity and acquires images of the illuminated portion of the cavity. The professional views the images, and assesses whether a polyp appears to be present in the illuminated portion.
Detection of a polyp is difficult because of the relatively complicated background that is the surface of the cavity. Consequently, because of the complicated background, even a trained professional may have difficulty in identifying a region as likely to comprise a polyp.